[Cardiac and vascular components of the systemic circulatory reaction to orthostasis].

The orthostatic test (OT) induced regular constrictor responses of the resistance vessels and less regular those of the capacitance vessels under conditions of extracorporeal circulation (by passing the left ventricle) in anesthetized cats. Responses of the resistance vessels were eliminated by ganglionic blockade, while blood pooling rised only in half of experiments under these conditions. In case of natural circulation, the ganglionic blockade entailed an obvious initial hypotension followed by lowering of compensatory elevation of arterial pressure (AP) while responses of the cardiac output to OT remained unchanged. By the method of extracorporeal circulation combined with the "working" heart significant lowering of the cardiac output to OT was achieved; this response was accompanied by constrictor responses of the resistance vessels. Compensatory responses of AP reveal themselves mainly by the vascular component of the systemic reaction.